Means for reproducing motion



Feb. 29, 1944, E BECHBERGER 2,342,637

MEANS FOR REPRODUCING MOTION Filed sept. 1o, 1941 2 Sheng-shea 1 u) ml f m q :Il i: C

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P. F'. BECHBERGER MEANS FOR REPRODUGING MOTION Filed Sept. l0, 1941 2 Sheets-Sheet 2 m mkg Patented Feb. 29, 1944 2,342,637 MEANS FOB REPRODUCING MOTION Paul F. Beehberger, Tenafiy, N. J., assignor to Bendix Aviation Corporation, Bendix, N. J., a corporation of Delaware Application September 10, 1941, Serial No. 410,343

24 Claims.

The present invention relates to means for reproducing motion, more particularly to means for reproducing angular motion at a remote point, and constitutes a novel improvement, adaptation and simplification of the structure of the invention disclosed in the co-pending application of Wladimir A. Reichel, Serial No.

344,795, illed July 10, 1940, now Patent No.4

2,269,602, dated Januaryr 13, 1942, which is assigned to the assignee of the present invention.

control of other objects if so desired.

with the core and windings.

synchronously.

devices.

l or repeaters located at points remote from said The apparatus of the present invention, like master magnetic compass, this being accomthat of the invention disclosed in the aforesaid plished by removing the magnet rotor of the Patent 2,269,602, is especially adapted for remote transmitter and placing the Wound stator in coindication; i. e., for measuring the value of a operative relation with the magnet of the comfactor at one -point by means of some suitable pass, whereby said compass magnet then funcmeasuring instrument and then transmitting tions as a rotor of the transmitter, and the use that value to and indicating it at another and of a separate rOtOr 01 0f a fOlOWiuD motor and remote point, but may also be utilized for remote relays is rendered unnecessary. Therefore, an-

' other object of the invention is to provide a In the aforesaid Patent 2,269,602, the apparanovel repeater system for magnetic Compasses, tus includes a transmitter and a remote receiver wherein the directional indication that is applied electrically connected together, the transmitter to the transmitter is derived from the compass and receiver consisting of a pair of substantially Without any mechanical connection to the rosimilar electromagnetic devices each of which tatable magnet System 0f the COI'nDaSs and withcomprises a stator having a core of magnetically out the use of any relays or follow-up motors. permeable material with a polyphase winding Another object of the invention is t0 Provide and a single phase winding thereon in inductive a novel magnetic compass repeater System relation with each other, and a rotor comprising wherein the transmission of the compass india poled magnet associated in magnetic relation cation t0 distant repeaters 0r indicators does one of the windnot interfere in any way with the operation of ings of the transmitter and the corresponding the compass itself. Winding of the receiver are energized by means A further Object is t0 provide a nevel masof a periodically varying current which may be netic compass repeater system, whereby it bean alternating current or a pulsating direct cur- 3f comes unnecessary to alter or modify the comrent, and then when the poled magnet rotor of pass structure in any way when the transmitter the transmitter is rotated the poled magnet rotor is adapted to the compass. of the receiver will rotate correspondinglyn and The above and other objects and advantages of the invention will appear more fully herein- In accordance with the present invention, the after from a consideration of the detailed den polyphase winding and the single phase winding scription which follows, taken together with the of each of the devices are replaced by a single accompanying drawings wherein two embodiwinding or coil having a plurality of taps, and ments of the invention are illustrated by way the tapped winding of the transmitter stator is of example. electrically connected to corresponding taps of however; that the drawings are for purposes of the winding of the receiver stator, thereby elimiillustration only, and are not to be construed nating a winding without eliminating its funcas deiining the limits of the invention, reference tion, and simplifying the structure of the prior being had for this purpose to the appended claims.` Accordingly, one 0f the ObJ'eCtS 0f the invention 5D In the drawings. wherein like reference charis to provide a novel and improved system for acters refer tolike parts in the three views, reproducing motion at a remote point and em- Fig. 1 is a more or less diagrammatic-illustrabodying a pair of novel electromagnetic devices tion of one embodiment of the invention as apone of which is a transmitter and the other a plied to the production of a remote indication by receiver, and each ofwhich comprises a wound stator cooperating with a magnet rotor having no windings thereon, thereby eliminating brushes, slip rings and commutators.

In accordance with the present invention, it has also been found that the system is readily adapted to remote reading Compasses or magnetic compass repeaters, whereby the directional indication of a master magnetic compass is repeated or reproduced by one or more indicators It is to be expressly understood,

an altimeter, for example, and shows a transmitter and one receiver with their magnetic and electric circuits and connections;

Fig. 2 is a similar illustration of another emmitter 3 and a distant receiver 4 electrically connected to said transmitter in a manner which will be described hereinafter. It is to be understood of course that two or mre such receivers may be connected to said transmitter 3. 1

The transmitter comprises a stator and a rotor in cooperative relation, the stator consisting of a core 5 in the form of a laminated annulus or ring of highly permeable magnetic material such, for example, as Permalloy or Mumetal," having wound thereon a single coil 6 which is tapped at two or more points as, for example, at points 1 and 3 intermediate the ends 9 and IU amaca? It will be seen that the tapped points l.. 8 of coil 6 and the tapped points I4, l5 of coil I3 constitute, in eiect, polyphase connections, while theA ends 9, I0 and I6, I1 of said coils constitute single phase connections. In other words, the entire length of each coil is single phase so that said coils correspond to the single phase windings shown in the aforesaid application Serial No. 344,- 795, While the tapped'sections, in`efi'ect, divide the coils into sections that are one hundred twentyr degrees (120) apart and correspond to the polyphase windings shown in said application Serial No. 344,795. Thus, coils 6 and I3 function as auto-transformers having input terminals 9, I0 and I6, Il and output terminals l, 8 and I4, I5.

Means are now provided for rotating the rotor II of the transmitter 3 in accordance with and of said coil, the ends and the tapped points being angularly spaced one hundred twenty degrees (120) apart along the circumference of the core 5.

Concentricallyarranged within the stator core 5 of the transmitter and in magnetic relation therewith and with the coil 6 is a rotor il in the form of a magnetic member of marked polarity as, for example. a rotatable permanent magnet having north and south poles as indicated at N and S, providing a uni-directional magnet iiux which enters the core 5. The rotor II, in the present instance, is shown in the ,form of a disc magnet one-half of which constitutes the north pole and the other half the south pole.

The receiver 4 shown in Fig. 1 is located at the remote point and likewise comprises a stator and a rotor in cooperative relation, the stator consisting of a core I2 in the form of a laminated annulus or ring of highly permeable material, having wound thereon a single coil I3 which is also tapped at two or more points as, for exam- (120) apart along the circumference of the core The rotor of the receiver likewise comprises a ple, at points I4 and I5 intermediate the ends I6 rotatable permanent magnet I8 in the form of a disc one-half of which constitutes a north pole and the other half a south pole, said magnet providing a uni-directional magnetic flux which enters the core I2.

The ends 9, I0 of the coil 6 of the transmitter stator are electrically connected to the ends i6, I'l of the coil I3 of the receiver stator by means of the leads I 9 and 20, respectively, While the tapped points 1 and 8 of coil 6 are electrically connected to the corresponding tapped points I4 and I5 of coil I3 by means of leads 2|- and 22 respectively.

Both coils 6 and I3 are energized by either a single phase alternating current or a pulsating4 in response to the factor to be measured and to be indicated at the distant receiver 4 in substantially the same manner as disclosed in the aforesaid application Serial No. 344,795. Such means comprise, in the present instance, a drive shaft 26 having one end connected to the magnet rotor Ii and carrying at its other end a pinion 2l meshing with a gear sector 28 which is vpivoted at 2S and connected to a measuring instrument such, for example, as an evacuated bellows or altimeter aneroid 30 by means of a link 3l and a lever 32. Thus, upon expansion and contraction of the evacuated bellows or aneroid 30, the gear sector 28 drives the pinion 21 to rotate the magnet rotor II in a direction and amount corresponding to the direction and amount of movement of the evacuated bellows or aneroid 30 in accordance with changes in barometric pressure caused by changes in altitude in the present instance, it being understood, of course, that any other type of measuring instrument can be substituted for said aneroid 30.

The magnet rotor I8 of the receiver 4 is drivably connected to an indicator 33 in any suitable manner as by means of a shaft 34 one end of which is connected to the magnet rotor I8 and the other end of which is connected to a pointer 35 which cooperates with a suitable scale 36 of the indicator 33.

Upon energization of the coils 6 and I3 of the transmitter and receiver, respectively, through their ends 9, lII) and I5, Il from the source 23, voltages are generated in the tapped sections of said coils due to the periodic reversal of the ilux produced in the cores 5 and I2 by the periodi` cally varying current flowing in coils 6 and I3 from the source 23. During one-half cycle of the exciting current from source 23 the periodically varying iiux opposes the uni-directional iiux of the magnet rotors II and I8 in one-half of the cores 5 and I2 and, at the same time, aids said uni-directional ux in the other half of the said cores, while during the other half cycle of said exciting current said periodically varying flux aids the uni-directional flux of the magnet rotors II and I8 in the one-half of the cores 5 and I2 and, at the same time, opposes said uni-directional iiux in the other half of said cores, as fully explained in the aforesaid application Serial No. 344,795. The voltages thus generated in the sections of coils 6 and I3 by the flux variation in cores 5 and I2 are even harmonics of the fundamental frequency of the exciting current from source 23.

When the rotors I I and I8 are in step, the even harmonic voltages in the sections of coil 6 are exactly equal to the even harmonic voltages in the sections of coil I3 but are in an opposite direction and, as a result, there is no current now in the connecting leads I3, 2l, 2| and 22 by which the sections of coil 8 of the transmitter are connected to the sections of coil I3 of the receiver. If, however, the magnet rotor I I of the transmitter is angularly displaced by aneroid 30, the secondary voltages in the coil 8 will no longer be equal to the secondary voltages in coil I3, and current .will flow in the leads I3, 20, 2I and 22 connecting the sections of coil 8 and the sections of coil I 3, thereby producing a resultant magnetic field at the receiver core I2, which reacts with the field of the receiver magnet rotor I8 to produce a torquewhich rotates Said magnet rotor I3 and brings it into step with the magnet rotor II of the transmitter in substantially the same manner as set forth in the aforesaid application Serial No. 344,795. Rotation of the receiver rotor I8 actuates the pointer 38 of the indicator 33 to show; the amount of angular displacement of transmitter rotor II by the aneroid 3II in terms of altitude. Thus, the motion of the transmitter rotor I I is reproduced at the distant point by the receiver rotor I8 and, hence, the altitude measured by the aneroid 30 is repeated and indicated at the remote point by the indicator 33.

Referring now to Fig. 2 of the drawings, the

invention is shown applied to a magnetic com-V pass, whereby the directional indication of said compass is repeated or reproduced by an indicator at a point remote from the compass without any mechanical connection or coupling between the rotatable magnet of the compass and l without interfering in any way with the operation of the compass. The repeater system, as shown, comprises a master magnetic compass 31 having a compass bowl 38 in which is rotatably mounted the compass magnet 39 carried by a vertical shaft 4II journalled in an upper bearing 4I and a lower bearing 42 inside of said bowl 38 'so that said magnet 39 may rotate under the influence of the earths magnetic field in the usual manner.

In this embodiment the compass magnet 33 serves as the rotor of the transmitter, thereby eliminating the rotor II shown in Fig. 1 `and, therefore, the stator core 5 and coil 6 are arranged in such a manner that they surround `the compass bowl 38 of the compass so that they are concentric with the compass magnet 39, but the coil 8 is connected to the coil I3 of the receiver in the same manner as in Fig. 1.

The ystators of the transmitter and receiver shown in Fig."2 are substantially the same as in Fig. 1 except that they are provided with laminated annular members 43 and 44 of magnetic material, which serve to provide a return path for the second harmonic flux produced in the 4core members 5 and I2, the laminations being indicated generally by the reference numeral 41.

In Fig. 2 the coils 8 and I3 are energized by a uni-directional current from a suitable source 48 as well as by an alternating current from the source 23. The direct current flowing in the coils 8 and I3 sets up a uni-directional flux in tiie cores i and I2, which flux is aided by the flux of the rotor magnets 33 and I8 in one portion of said cores and is opposed in the diametrically opposite portion of each core. Thus,

the magnetic reluctance to the periodically vary-V ing portion of the flux in the cores is not uniform throughout, while the ampere-tums-magnetiz-- ing-force is uniform around the cores and is accentuated by the return path members 43 and 44.

Instead of providing a separate direct current source 48, a portion of the alternating current from source 23vmay be rectified and then supplied as direct current to the coils 8 and I3.

In Fig. 3 is shown another embodiment of a transmitter of a magnetic compass repeating system in which the transmitter stator is located beneath the compass bowl 38 of the compass, but the coil 8 is connected to stator coil (not shown) by leads 2| and 22 and is energized from the source of current (not shown) by leads I9 and 28 as in Figs. l and 2. With this arrangement, the transmitter stator may be made smaller than in the embodiment shown in Fig. 2.

There is thus provided a novel and relatively simple apparatus for reproducing motion at a remote point, and one which readily lends itself to a use as a magnetic compass repeater without the use of follow-up motors or relays and without having to alter the structure of the master magnetic compass, the directional indication of which is to be repeated at the remote point. The apparatus involves a minimum number of parts, is small, compact and light in weight, which makes it possible of manufacture in large quantities at low cost, and makes it vparticularly suitable for installation on aircraft for remote indication of engine temperature, fuel pressure, fuellev'el, oil pressure, etc. I

Although three embodiments of the invention have been illustrated and described as applied to an altimeter and a compass, it may be aption of the compass magnet 39 takes place in azimuth under the influence of the earths magnetic field, such rotation is reproduced at the remote point bythe magnet rotor I8 of the receiver and is indicated by the pointer 35 on the scale 36 which is calibrated as a compass rose to indicate the direction of the earths magnetic plied to'various other uses where remote indication or vremote control is desired, and variousv changes and modifications in the construction and relative arrangement of the parts, which will now appear to those skilled in theart, may be made without departing from the scope of the invention. Moreover, although in the illustrated embodiments only one receiver is shown connected to the transmitter, two or more such receivers may be connected to said transmitter in parallel with said one receiver without impairing the function of the systemk in any way. Reference is therefore to be had to the appended claims for a definition of the limits of the invention.

What is claimed is:

l. A magnetic compass repeating system comprising a magnetic compass having a magnet rotatable under the influence of the earths magfield as determined by the compass magnet 3S at the transmitter.

The compass 3'I may be provided with a conventional magnetic deviation compensator of any suitable type at the top thereof, which -s netic field, an annular core member of magnetically permeable material coaxially arranged in influencing relation with said compass magnet, whereby a uni-directional flux is induced in said core member by said magnet, coil means on said core member and having polyphase connections and a single phase connection, a second annular core member of magnetically permeable material located at a point remote from said compass, coil means on said second core member and `also having polyphase connections and a single phase connection, the polyphase connections of the first coil means being electrically' connected to the polyphase connections of the second coil means in corresponding phase relation, a source of periodically varying current connected to the single phase connection of both of said coil means, and a rotatable magnet associated with the second core member for actuation by the reaction between the magnetic eld of said magnet and the magnetic ileld produced bythe coil means oi the second core member uponrotation of the compass magnet.

2. A magnetic compass repeating system com prising a magnetic compass having a magnet rotatable under the iniiuence of the earthsl magnetic iield, an annular core member of magnetically permeable material coaxially arranged in influencing relation with said compass magnet, whereby a uni-directional ux is induced in said core member by said magnet, coil means on said core member and having polyphase connections and a single phase connection, a second annular core member of magnetically permeable material located at a point remote from said compass, coil means on said second coil member and also having polyphase connections and a/ `single phase connection, the-polyphase connec# tions of the rst coil means being electrically connected to the polyphase connections of the second coil means in corresponding phase relation, a source of periodically varying current connected to the single phase connection of both of said coil means, a rotatable magnet associated with the second core member for actuation by the reaction between the magnetic field of said magnet and the magnetic eld produced by the coil means of the second core member upon rotation of the compass magnet, and indicating means actuated by the rotatable magnet at the second core member.

3. An electromagnetic device adapted for use as a transmitter or receiver and arranged for electrical connection to a similar device functioning respectively as a receiver or transmitter, said device comprising a stator including an annular core of magnetically permeable material,

an auto-transformer coil wound on said core,

said coil having connections atv its ends for energizing said coil by a periodically varying current and having a plurality of other connections intermediate its ends for connecting said coil to a corresponding plurality of connections of av coil of a similar device, and a rotor comprising a poled magnet, associated in magnetic relation with said core and said coil.

4. A magnetic compass repeating system comprising a magnetic compass having a magnet rotatable under theinuence of the earths magnetic eld, an annular core member of magnetically permeable material coaxially arranged in inuencing relation with said compass magnet, whereby a uni-directional flux is induced in said core member by said magnet, coil means on said core member and having polyphase connections and a single phase connection, a second annular core member of magnetically permeable material located at a point remote from said compass, coil means on said second core member and also having polyphase connections and a single phase connection, the polyphase connections of the rst coil means being electrically connected to the polyphase connections of the second coil means in corresponding phase relation, a source or alternating current connected to the single phase connection of both of /said coil means, and a rotatable magnet associated with said second core member for actuation by the reaction between the magnetic field of said magnet and the magnetic field produced by the coil means of the second core member upon rotation of said compass magnet.

5. A magnetic compass repeating system comprising a. magnetic compass having a magnet rotatable der the influence of the earths mag- -netic field,.an annular core member of magnetimeans in corresponding phase relation, a source of alternating current connected to the single l phase connection of both of said coil means,

irl

a rotatable magnet associated with said second core member for actuation by the reaction between the magnetic eld of said magnet and the magnetic eld produced by the coil means of the second core member upon rotation of said compass magnet, and indicating means actuated by the rotatable magnet at the second core member.

6. An electromagnetic device adapted for use asa transmitter or receiver and arranged for f electrical connection` to a similar device functioning respectively as a receiver or transmitter, said device comprising a stator including an annular core of magnetically permeable material, an auto-transformer coil wound on said core, said coil having connections at its ends for `energizing said coil by a periodically varying current and having a plurality of other connections intermediate its ends for connecting said coil to a corresponding plurality of connections of the coil of a similar device, and a rotor comprising a circular magnet having north and south poles and rotatably mounted inside of said core in magnetic relation therewith and with said coil.

7. Means for transmitting angular motion from one point to another point, comprising a iirst relatively stationary annular core of magnetically permeable material at the irst point,

' a coil wound on said core and having a plurality of taps, a rotatable magnet in magnetic relation with said core and coil, a second-relatively stationary core of magnetically permeable material at said other point, a coil wound on said second core and also having a plurality of taps corresponding ytol the number of taps on the coil of said first core, a rotatable magnet in magnetic relation with said second core and coil, means electrically connecting the taps of said iirst coll to the corresponding taps of said second coil, and a source of periodically varying current connected to energize both of said coils whereby, upon rotation of the magnet at the iirst core, the magnet at the second core is correspondingly rotated.

8. Apparatus for electrically transmitting the indications of a magnetic compass to a remote point without the use of a follow-up motor or other electro-mechanical torque-amplifying device, comprising a magnetic compass having a magnet rotatable under the influence of the earths magnetic neld, an electrical transmitting device at the compass and having a stator in direct inductive relation with said compass magnet, whel'eby the latter constitutes the rotor oi' said transmitting device so that separate coupling means between the compass and transmitting-device are eliminated, an electrical receiving device at the remote point and having a rotor and a stator in inductive relation with each other, indicating means drivably connected to the rotor of said receiving device for actuation thereby, and means electrically connecting said transmitting device to said receiving device independently of any follow-up motor or other electro-mechanical torque-amplifying device, whereby angular movement of said compass magnet causes corresponding angular movement of the rotor of said receiving device to actuate said indicating means.

9. Apparatus for electrically transmitting the indications of a magnetic compass to a remote point without the use of a follow-up motor, comprising a magnetic compass having a magnet rotatable under the iniluence of the earths magnetic ileld, an electrical transmitting device at the compass and having. a coil wound stator in direct inductive relation with said compass magnet, whereby the latter iunctions as the rotor of said transmitting device, an electrical receiving device at the remote point and also having a coil wound stator and a rotor consisting of a rotatable magnet in cooperative relation therewith, a source of periodically varying current, A

means electrically connecting said source to the coil wound stator of both the transmitting device and the receiving device, means electrically connecting the coil wound stator of the transmitting device to the coil wound stator of the receiving device, whereby the angular movement of said'compass magnet causes corresponding angular movement of the magnet rotor of said receiving device, and indicating means connected to the magnet rotor of said receiving device for actuation thereby.

10. In combination, a transmitter comprising a first core member of magnetically permeable material, a coil on said core member and having a plurality of taps, a rotatable magnet in innuencing relation with said core member for inducing a magnetic rlux therein, a receiver comprising a second core member of magnetically permeable material, a poil on said second core member and also having a plurality of taps-corresponding to the number of taps on said rst coil, the taps of said first coil being electrically connected to the correspondingv taps of said second coil, a source of periodically varying current connected to energize both the first coil and the second coil, and a rotatable magnet associated with said second core member and coil for actuation by the reaction between its own field and the field produced by said second coil upon rotation of the magnet at the transmitter.

11. Apparatus for electrically transmitting the indications of a magnetic compass to a re-` in magnetic relation with said compass magnet, whereby the latter serves as a rotor of said transmitter for producing electrical energy in said stator in accordance with the amount and direction of relative angular movement between said stator and rotor, an electrical receiving device at the remote point and having a rotor and a stator associated in cooperative relation with each other, indicating means at said receiving device drivably connected to the rotor thereof for actuation thereby, and means electrically connecting said transmitting device to said receiving device independently of any follow-up motor or other electro-mechanical -torque-amplifying device-for controlling angular movement of the receiver rotor by and in accordance with the relative angular movement of said compass magnet to actuate said indicating means.

12. An electromagnetic device adapted for use as a transmitter and arranged for electrical connection to a remote receiver, comprising a stator having anannular core oi' magnetically permeable material, an auto-transformer coil wound on said core, said coil having connections at its ends for energizing said coil by a periodically varying current and having a plurality of other connections for connecting said coil to a corresponding plurality of connections of a coil of the remote receiver, and a rotor comprising a poled magnet associated in magnetic relation with said core and coll.

13. An electromagnetic device adapted for use as a transmitter .or receiver, comprising a stator having a core of magnetically permeable material, an auto-transformer coil on said core and having a plurality of connections intermediate its ends, said coil being arranged for energization by a periodically varying current, and a rotor comprising a poled magnet associated in magnetic relation with said core and coil.

14. In combination, a magnetic compass having a magnet rotatable under the influence of the eartis magnetic `field, an electrical transmitting device at the compass and having a wound stator in magnetic relation with said compass magnet, whereby the latter serves as a rotor of said transmitting device for producing electrical energy in said stator in accordance with the amount and direction of relative angular movement between said stator and magnet, a remote electrical receiving device having a rotor and a stator associated in cooperative relation with each other, means at said receiving device drivably connected to the rotor thereof for actuation thereby, and means electrically connecting said transmitting device to said receiving device independently of any follow-up motor or other electro-mechanical torque-amplifying device, for controlling angular movement of the receiver rotor by and in accordance with the relative angu- -lar movement of said compass magnet.

15. In combination, a transmitter comprising rst core -means of magnetically permeable material, a winding on said tlrst coremeans having a plurality of connections intermediate its. ends, a rotatable magnet in influencing relation with said core means for inducing a magnetic ilux therein, a receiver comprising second core means of magnetically permeable material, a winding on said second core means and also'having a plurality of connections intermediate its ends, the connections of said ilrst winding being electrically connected to corresponding connections of said second winding, a source of periodically varying current connected to energize both of said windings, and a rotatable magnet associated in magnetic relation with said second core means and winding for actuation by the reaction between lts own eld and the ileld produced by said second winding upon rotation of the magnet at the transmitter.

16. In combination, a transmitter comprising first core means of magnetically permeable material arranged to be traversed by a uni-directional magnetic field for inducing a magnetic iiux therein, a winding on said ilrst core-means having a plurality of connections intermediate its ends, a receiver comprising second core means of magnetically permeable material, a winding on said second core means and also having a plurality of connections intermediate its ends, the connections o1' said iirstwinding being electrically connected to corresponding connections of said second winding, a source o'i periodically varying current connected to energize both of said windings, and a rotatable magnet associated in magnetic relation with said second core means and winding for actuation by the reaction between its vown ileld and the eld produced by said second windingupon relative angular displacement between said first core means and the ileld by which itis traversed.

17. An electromagnetic device adapted for use as a transmitter or receiver, comprising relatively stationary core means of magnetically permeable material, coil means on said core means and having at least three connections, certain of said connections being arranged for connection to a source of periodically' varying current, a rotatable magnet associated in magnetic relation with said core means and coil means, and shielding means of magnetic material for shielding said device to prevent interaction with external magnetic ilelds, said shielding means also serving to provide a return magnetic path for the magnetic ilux induced in said core means by said rotatable magnet.

18. An electromagnetic device adapted for use as a transmitter or receiver, comprising a stator having a core of magnetically permeable material, an auto-transformer coil on said core and having a plurality of connections intermediate its ends, said coil being arranged for energization by a source oi' periodically varying current, a rotor comprising a poled magnet associated in magnetic relation with said core and coil, and shielding means of magnetic material for shielding said device to prevent interaction with external magnetic iields, said shielding means also serving to provide a return magnetic path for the magnetic ilux induced in said core bysaid poled magnet.

19. An electromagnetic device adapted for use as a transmitter or receiver, comprising relatively I stationary core means of magnetically permeable material, an autotransformer coil on said core means and having a plurality of connections invide a return magnetic path for the magnetic flux induced in said core means by said rotatable magnet.

20. An electromagnetic transmitter comprising relatively stationary core means of magnetically permeable material adapted to be traversed by a uni-directional magnetic ileld, an auto-transformer coil on said core means and having a plurality of connections intermediate its ends, said coil being arranged ior energization by a periodically varying current for inducing alternating current voltages therein when a uni-directional magnetic ileld traverses said core means. and shielding means oi magnetic material for shielding said device to prevent interaction with, undesirable magnetic ilelds. i

21. In combination, a transmitter comprisin ilrst core means of magnetically permeable material, a winding on said first core means having a plurality of connections intermediate its ends, a movable magnet in inuencing relation with said core means for inducing a magnetic iiux therein: a receiver comprising second core means of`magnetically permeable material, a winding on said second core means and also having a plurality of connections intermediate its ends, the connections of said rst winding being electrically connected to the corresponding connections of said second winding, a source of periodically varying current connected to energize both of said windings, and a movable magnet associated in magnetic relation with said second core means and winding for actuation by the reaction between its own eld and the eld produced by said second winding upon movement of the rst magnet relative to said rst core means.

22. In combination, a transmitter comprising irst core means oi magnetically permeable material arranged to be traversed by a uni-directional magnetic field for inducing a magnetic ilux therein, a winding on said ilrst core means having a plurality of connections intermediate its ends, a receiver comprising second core means oi magnetically permeable material, a winding on said second core means and also having a plurality of connections intermediate its ends, the connections of said ilrst winding being electrically connected to the corresponding connections of said second winding, a source of periodically varying current connected to energize both of said windings, and a movable magnet associated in magnetic relation with said second core means l and 'winding for actuation by the reaction between its own ileld and the eld produced by said second winding upon relative movement between said irst core means and the ileld by which it is traversed.

23.An electromagnetic device adapted for use as a transmitter or receiver, comprising relatively stationary core means of magnetically permeable material, a winding on said core means and having a plurality of connections intermediate its ends, said coil being arranged for energizatlon by a periodically varying current, and a movable member comprising a poled magnet associated in magnetic relation with said core ineans and winding and movable with respect thereto.

`24. A magnetic compass repeater system for transmitting the relative angular movements of the compass magnet to a remote point without the use of a follow-up motor or other electros mechanical torque-amplifying device, comprising a magnetic compass having a magnet rotatable under theiniluence oi the earths magnetic ileld, an electrical transmitting device at the compass and having a wound stator in magnetic relation with said compass magnet, whereby the latter functions as a rotor of said transmitting device for producing electrical energy in said stator in accordance with the amount and direction of relative angular movement between said stator and compass magnet, an electrical receiving device at the remote point and having a. rotor and a stator associated in cooperative relation with each other, means at said receiving device drivably connected to the rotor thereof for actuation thereby. and means electrically connecting said transmitting device and said receiving device independently oi' any follow-up motor or other electro-mechanical `torque-amplifying device', for controlling angular 5 compass magnet.

PAUL F. BECHBERGER. 

